The use of gas for retarding, controlling, killing or preventing microbiological contamination (e.g., bacteria, fungi, viruses, mold spores, algae and protozoa); retarding, preventing, or controlling biochemical decomposition; controlling respiration, deodorizing and/or retarding and preventing chemotaxis to name a few, is known. Such gases include, but are not limited to, chlorine dioxide, sulfur dioxide, nitrogen dioxide, nitric oxide, nitrous oxide, carbon dioxide, hydrogen sulfide, hydrocyanic acid, and dichlorine monoxide. For example, the use and efficacy of chlorine dioxide is documented and discussed in various publications such as G. D. Simpson et al., A Focus on Chlorine Dioxide, An Ideal Biocide (visited Feb. 5, 2000) http://clo2.com/readings/waste/corrosion.html, and K. K. Krause, DDS et al., The Effectiveness of Chlorine Dioxide in the Barrier System (visited Feb. 5, 2000) http://www.dentallogic.com/dentist/effects.htm.
In particular, chlorine dioxide has been found to be useful as a disinfectant, antiseptic and sanitizer. It is used, e.g., to disinfect drinking water and various water supplies. In addition, chlorine dioxide finds use as a bleaching agent for flour, fats and textiles. Chlorine dioxide also has shown great utility as an antiseptic for treating metal and plastic surfaces, as well as other substrates such as countertops, meat processing and packaging equipment, and dental and medical instruments and devices.
One disadvantage of the prior art methods for generating chlorine dioxide gas generally is that unsatisfactory levels of by-products or reactants remain as a residue. For example, in the case of chlorine dioxide gas, the byproduct chlorite leaves residues on food handling equipment and medical and dental surfaces. Human contact with such residues should be avoided or substantially minimized according to FDA and EPA regulations.
Another requirement in the food handling and related industries is the need for raw materials or ingredients that are safe to handle in the preparation of the disinfectant. The requirement is for the inclusion of reagents that are safe to use and, after generating chlorine dioxide, produce side products that are non-toxic and/or biodegradable.
Also, although it has great beneficial characteristics, chlorine dioxide can not be transported commercially as a concentrated gas for its use and instead has been generated at the site where it is used. Thus, an on-site gas generation plant typically is required to generate the gas that is then delivered to the fluid in which it will be used. Such apparatus takes up space and represents a significant added expense. Moreover, even when prior art apparatus do not require a separate gas generation component e.g., those shown in European Patent Publication No. 0 571 228 for sulfur dioxide generation, such apparatus are still undesirable because controlling the amount of gas generated, the efficiency of the generation, and the duration of the gas generation has proven difficult, if not unsuccessful.
There exists a need for the controlled, on-site generation of gases, such as sulfur dioxide and chlorine dioxide, which can be produced safely, efficiently and economically, without the necessity for a separate generation plant or unwanted by-products. The present invention addresses these needs.